1. Field of the Invention
The present invention relates to a spare tire carrier, and more particularly to a spare tire carrier mounted on a truck or a freight car.
2. Description of the Prior Art
Generally, space is limited in an automobile, particularly a truck or a freight car for accommodating a spare tire, such that a separate carrier is mounted underneath the automobile for accommodation of the space tire.
The spare tire carrier includes, as illustrated in FIGS. 4 to 6, a housing 50 fixedly mounted underneath an automobile and formed in "U" shape, a roller assembly 53 rotatably mounted to the housing 50 via a rotary shaft 51 and wound by a wire 52, and a hitching device so constructed as to enable the roller assembly 53 to rotate to a wire's winding direction and to be hitched to a wire's unwinding direction. The roller assembly 53 is constructed such that first and second roller plates 54 and 55 are coupled by a pin 56 and the wire 52 is wound therebetween.
Furthermore, the hitching device is provided with a gear plate 58 coupled to one side of the first and second roller plates 54 and 55 and formed with a first gear 57 having a predetermined diameter and a rotary plate 61 formed with a second gear 59 having a diameter smaller than that of the first gear 57 and eccentrically inserted with the first gear 57 and rotatably supported by an eccentric cam 60 of the rotary shaft 51.
At this location, the wire 52 is provided with an oval accommodation plate 62 at a longitudinal end thereof for a spare tire (T) to be accommodated therein and a guide plate 63 for preventing the wire 52 from being dislodged from the roller assembly 53, where the rotary plate 61 is resiliently supported by a spring 64 to be pulled downwards at all times. The accommodation plate 62 is protrusively formed with a plurality of support ribs 65 in order to support a position of the spare tire (T).
Now, operation of the spare tire carrier thus constructed will be described.
First of all, the spare tire (T) is inserted through a smaller diameter of the oval accommodation plate 62 to cause the support rib 65 to support the spare tire (T). Under this state, when a rotating force is input via the rotary shaft 51, part of the second gear 59 at the rotary plate 61 is meshed with the first gear 57 and rotated.
At this time, the rotary plate 61 is rotated by the eccentric cam 60 formed at the rotary shaft 61, where the second gear 59 is meshed towards the rotating direction of the first gear 57 and rotated.
When the first gear 57 is rotated by the rotary plate 61, the gear plate 58 formed with the first gear 57 couples with the roller assembly 53 to cause the roller assembly 53 to rotate and to make the wire 52 wind or unwind. At this time, if the force rotating the rotary shaft 51 is excessive, the rotary plate 61 copes with the resilience of the spring 64 by being rotated clockwise, by which the excessive force is absorbed to prevent breakage of the first and second gears 57 and 59.
Under a state where the wire 52 is wound, the wire 52 remains wound even though it is pulled downwards by the load of the spare tire (T). The reason the wire 52 is not unwound is that the first and second gears 57 and 59 are eccentrically meshed. In other words, if the force is applied towards the rotary shaft, the wire 52 is not disentangled.
In other words, only if the force is applied towards the rotary shaft 51, the roller assembly 53 is rotated to wind or unwind the wire 52.
However, there is a problem in that, when the first and second roller plates are adhered and coupled by a pin in order to wind the wire to which the force is applied, the pin cannot restrain the first and second roller plates if an excessive force is applied via the wire, such that the housing and roller plate are widened to cause the wire to be caught in between the housing and the roller plate, resulting in an inoperable state.
In other words, the first and second roller plates are relatively easily widened when an excessive force is applied to the wire because the pin only restrains the position of the first and second plates and the housing apply a pressure for adhering and coupling the first and second roller plates, thereby causing the wire to be wedged therebetween.
Furthermore, there is another problems in that because the support rib at the accommodation plate where the spare tire is accommodated is relatively weak, and when the spare tire is frequently replaced, the support rib can be easily broken or deformed.
There is still further problem in that, because the rotary plate, provided to prevent breakage of the first and second gears when an excessive force is applied toward the rotary shaft, is rotated around the eccentric cam and is operated at a part relatively long distanced from the part where the excessive force is applied, response to the operation is slow, and if the resilient adjustment of the spring is not accurate, operating force can be deteriorated.